The objective of the project is to examine the hypothesis that cellular differentiation and malignant transformation are accompanied by expression of specific cell surface proteins. The surface proteins will be analyzed by a newly developed two-dimensional gel electrophoresis system. The final goal of the proposal during the period of grant support is to analyze and compare surface proteins of the normal and T/t locus mutant mouse embryos. The recessive t mutants of homozygous lethal type are uniquely suited for this project since 1) they interfere with development of embryos at six specific stages, 2) they interfere with the further differentiation of ectoderm, 3) they are expressed as the surface antigens, and 4) a number of mutant strains are available. I propose to utilize teratoma lines of T/t locus mutants as a means to amplify a homogeneous population of embryonic cells. The dynamics of cell surface protein organization also have obvious significance in development and neoplasia. To approach this aspect, I have chosen to study the cyclic AMP-dependent reverse tranformation phenomenon of Chinese hamster ovary (CHO) cells as model system, since the mouse embryo system is far too complicated at this stage of research development. With the CHO cells, cyclic AMP-dependent aggregation of a surface protein (M.W. 65,000) and appearance of a new surface protein species (M.W. 80,000) were discovered. Detailed characterization of the mechanism of surface protein aggregation and expression should elucidate some of the basic principles of the role of surface proteins in differentiation and transformation.